I tend to switch raqs before the grips need replacing usually, unless I change out to a leather one to add weight or just 'cause. The last ones I remember needing to replace were my old Ncode 6.1's 5 yrs ago.

I use Gamma Supreme overgrips. If I'm playing frequently, I'll wear through the top layer and the fabric underneath will give me good traction for a while. If I play only now and then, the dirt from my hands will mix with the tacky surface and make it feel gummy. I have some Dunlop Viper overgrips on order. I wonder if I'll be able to adjust.